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But Use this code...
.g-owlcarousel-feature-slider .owl-item .item .g-owlcarousel-item-image::before {
content: none;
}
To create a custom CSS compatible with Gantry 5 please read this
http://docs.gantry.org/gantry5/tutorials/adding-a-custom-style-sheet
.
Remember to recompile CSS from base outline too.
Regards, Mark.